13x15x6" Heavy Duty Double Wall Cardboard Boxes 10pk | eBay
Box Partners Shipping Boxes, 10"L x 10"W x 6"H, Double Wall Boxes, Pack of 15 (HD10106DW) | Quill.com
Amazon.com: BOX USA 25 Pack of Heavy-Duty Double Wall Corrugated Cardboard Boxes, 9" L x 9" W x 6 1/2" H, Kraft, Shipping, Packing and Moving : Industrial & Scientific